Generation of Bona Fide Fully Integrated Human Post-Implantation Structured Embryo Models (SEM) Derived Ex Utero Solely from Genetically Unmodified Naïve (HENSM) Pluripotent Stem Cells

In this protocol we describe a detailed step-by-step protocol for the derivation of fully integrated human Stem-cell-derived Structured Embryo Models (SEMs) solely form transgene-free genetically unmodified naïve cells expanded in HENSM condition. This 8-day protocol opens the possibility of modeling the architectural organization of all known lineages and compartments of early post-implantation stage human embryos up to day 13-14. The latter bona fide model system allows reconstituting and visualizing structures such as embryonic disc, hypoblast, bilaminar disk formation, epiblast lumenogenesis, polarized amniogenesis, anterior-posterior symmetry breaking, anterior visceral endoderm (AVE) formation, PGC specification, visceral and parietal endoderm as part of yolk sac formation, extra-embryonic mesoderm expansion that defines a chorionic cavity, a connective stalkand secondary yolk-sac (SYS) formation, a trophoblast surrounding compartment demonstrating syncytium formation with intercellular lacunaeand microvilli formation. This intergrated SEM (iSEM) system opens an opportunity to study the second week of human development which due to technical and ethical reasons has been unattainable for the research community.